Degradação fotoeletroquímica de corantes dispersos em efluente têxtil utilizando fotoanodos de Ti/TiO2

The degradation of disperses dyes in aqueous solution and in effluents from textile industry has been investigated by photoelectrocatalytic oxidation using nanoporous thin films electrodes of Ti/TiO2. Samples of dispersil black dye and dispersil blue dye after 300 min of photoelectrolyzed at applied potential of +1.0 V and UV irradiation exhibited 100% of discoloration and 90% and 64% reduction total organic carbon, respectively. The proposed method was applied with success in a textile industry effluent containing residues of these dyes, which after 300 min of treatment leads to reduction of 60% of COD and 64% removal of TOC.

Estudo da fotocatálise heterogênea sobre Ti/TiO2 na descoloração de corantes sintéticos

The main goal of this paper was to study the degradation of synthetic dyes using photoelectrocatalytic properties of particulate films of TiO2 supported on plates of titanium and stimulated by UV-Vis radiation. The dyes decolorizations were measured using spectrophotometric methods to verify which the conditions on Ti/TiO2 electrode was the best for the photoelectrodegradation of them. The results showed that decolorization rates were higher than 90% during a period of 270 min. FT-IR spectroscopy showed that intermediate substances were formed after the decolorization and N=N group/aromatic structures were preserved independently of the specific structure of the dyes.

A comparison of electrodeposited Ti/β-PbO2 and Ti-Pt/β-PbO2 anodes in the electrochemical degradation of the direct yellow 86 dye

The electrochemical performance of electrodeposited Ti/β-PbO2 and Ti-Pt/β-PbO2 anodes was galvanostatically evaluated (batch mode, 50 mA cm-2) to degrade the Direct Yellow 86 dye (100 or 200 mg L-1 in 0.1 mol L-1 Na2SO4 + 1.5 g L-1 NaCl), investigating the effect of pH and temperature. Similar results were obtained for both electrodes and the best conditions for removal of color and chemical oxygen demand are pH 7 and 40 °C, when 90% decolorization is attained by passing a charge of only ~0.13 A h L-1 and total mineralization is achieved with expenditure of ~5 kW h m-3.

Evaluation of the corrosion behavior of the al-356 alloy in NaCl solutions

Cellular metals are a new class of materials with promising applications and a unique combination of physical, chemical and mechanical properties. The Al-356 alloy is used to manufacture metal foams from NaCl preforms. Despite the usefulness of these materials, their performance may be affected by corrosion due to residual salt. This paper reports the study of the behavior of the Al-356 alloy in chloride solutions by electrochemical techniques in rotating disk electrode. The cathodic reaction of oxygen reduction is the crucial stage of process dissolution of the material, which shows that is the oxygen transport which limits the corrosion process.

Eletrodegradação de Ponceau 2R utilizando ânodos dimensionalmente estáveis e Ti/Pt

This paper reports the electrochemical degradation of the azo dye Ponceau 2R under galvanostatic electrolysis in the 1 to 200 mA cm-2 range at room temperature using dimensionally-stable anodes of oxygen (DSA-O2), chlorine (DSA-Cl2) and a titanium electrode of platinum coated with platinum oxide (Ti/Pt). The methodology applied was efficient for removing the color of the Ponceau 2R and the highest percentage removal of total organic carbon was obtained at 200 mA cm-2. Despite not having been observed complete mineralization, approximately80% removal of aromatic rings was estimated, resulting in drastic reduction of toxicity of the sample.

Microestrutura e resistência à corrosão do Ti c.p. soldado a laser utilizando em prótese sobre implantes

Foram realizados estudos para avaliar a microestrutura, a dureza e a resistência à corrosão do titânio comercialmente puro-Ti c.p. soldado por laser e utilizado na confecção de prótese sobre implantes. Verificou-se que na soldagem a laser a microestrutura apresentou três regiões distintas: o cordão de solda, a zona afetada pelo calor - ZAC e o metal base. O Ti c.p. possui microestrutura granular, a microestrutura do cordão de solda é mais refinada e de maior dureza do que o metal base. A ZAC obtida por este processo de soldagem foi relativamente pequena quando comparada com o processo de soldagem por brasagem. Os ensaios eletroquímicos mostraram que a região da solda apresentou menor resistência à corrosão em meio de NaCl 0,15 molL-1 à temperatura ambiente.

Electrochemical and physical characterization of Ni-Cu-Fe alloy for chlor-alkali hydrogen cathodes

This work describes the development of an alternative acetate bath for the electrochemical codeposition of Ni-Cu-Fe electrodes at low pH that is stable for several weeks and produces electrodes with good performance for chlor-alkali electrolysis. Physical characterization of the electrode surface was made using X ray absorption spectroscopy (XAS), scanning electron microscopy (SEM) and energy dispersive analysis (EDX). The evaluation of the material as electrocatalyst for the hydrogen evolution reaction (her) was carried out in brine solution (160 g L-1 NaCl + 150 g L-1 NaOH) at different temperatures through steady-state polarization curves. The Ni-Cu-Fe electrodes obtained with this bath have shown low overpotentials for the her, around 0.150 V at 353 K, and good stability under continuous long-term operation for 260 hours. One positive aspect of this cathode is that the polarization behavior of the material shows only one Tafel slope over the temperature range of 298 - 353 K.

Photoelectrocatalytical degradation of basic blue 41 dye using nanoporous semiconductor of Ti/TiO2

O presente trabalho investiga a degradação fotoeletrocatalítica do corante Azul Básico 41 (AB 41) amplamente utilizado na tintura de fibras sintéticas, utilizando um semicondutor Ti/TiO2 como fotoanodo. 100% de degradação foi obtida após 60 min de tratamento de 8,33x10-5 mol L-1 do corante em 0,1 mol L−1 Na2SO4, pH 2 sob densidade de corrente de 0,40 mA cm−2 e irradiação UV. Ainda foi obtido 80% de remoção de carbono orgânico total, cuja oxidação segue uma reação de pseudo-primeira ordem com constante de velocidade inicial de -0,040 mim-1 e uma eficiência de corrente de 51%. Os resultados são superiores á fotocatálise convencional nas mesmas condições sem a polarização do fotoanodo que leva a 65% de mineralização sob constante de velocidade de -0,024 mim-1.

Fracture modes and acoustic emission characteristics of hydrogen-assisted cracking in high-strength low-alloy steel weldment

The aim of the present paper is to study the relationship between the fracture modes in hydrogen-assisted cracking (HAC) in microalloied steel and the emission of acoustic signals during the fracturing process. For this reason, a flux-cored arc weld (FCAW) was used in a high-strength low-alloy steel. The consumable used were the commercially available AWS E120T5-K4 and had a diameter of 1.6 mm. Two different shielding gases were used (CO2 and CO2+5% H2) to obtain complete phenomenon characterization. The implant test was applied with three levels of restriction stresses. An acoustic emission measurement system (AEMS) was coupled to the implant test apparatus. The output signal from the acoustic emission sensor was passed through an electronic amplifier and processed by a root mean square (RMS) voltage converter. Fracture surfaces were examined by scanning electron microscopy (SEM) and image analysis. Fracture modes were related with the intensity, the energy and the number of the peaks of the acoustic emission signal. The shielding gas CO2+5% H2 proved to be very useful in the experiments. Basically, three different fracture modes were identified in terms of fracture appearance: microvoid coalescence (MVC), intergranular (IG) and quasi-cleavage (QC). The results show that each mode of fracture presents a characteristic acoustic signal.

Influence of duty factor on the die-sinking Electrical Discharge Machining of high-strength aluminum alloy under rough machining

The use of high-strength aluminium alloys as material for injection molding tools to produce small and medium batches of plastic products as well as prototyping molds is becoming of increasing demand by the tooling industry. These alloys are replacing the traditional use of steel in the cases above because they offer many advantages such as very high thermal conductivity associated with good corrosion and wear resistance presenting good machinability in milling and electrical discharge machining operations. Unfortunately there is little technological knowledge on the Electrical Discharge Machining (EDM) of high-strength aluminium alloys, especially about the AMP 8000 alloy. The duty factor, which means the ratio between pulse duration and pulse cycle time exerts an important role on the performance of EDM. This work has carried out an experimental study on the variation of the duty factor in order to analyze its influence on material removal rate and volumetric relative wear under roughing conditions of EDM process. The results showed that high values of duty factor are possible to be applied without bringing instability into the EDM process and with improvement of material removal rate and volumetric relative wear.

Longe de ti apagar nossas lembranças: as palavras e as preces no luto judaico

Este artigo propõe uma discussão inicial acerca do valor das preces nos rituais funerários e, sobretudo, como as palavras sagradas podem ser transformadas, para além do sentido primário que possuem, em importantes instrumentos no processo ritual post mortem. Neste sentido, o trabalho apresenta alguns detalhes sobre o ritual funerário judaico e suas preces, especialmente a partir da oração central, o Kaddish.

Adenovirus-mediated siRNA targeting TNF-α and overexpression of bone morphogenetic protein-2 promotes early osteoblast differentiation on a cell model of Ti particle-induced inflammatory response in vitro

Wear particles are phagocytosed by macrophages and other inflammatory cells, resulting in cellular activation and release of proinflammatory factors, which cause periprosthetic osteolysis and subsequent aseptic loosening, the most common causes of total joint arthroplasty failure. During this pathological process, tumor necrosis factor-alpha (TNF-α) plays an important role in wear-particle-induced osteolysis. In this study, recombination adenovirus (Ad) vectors carrying both target genes [TNF-α small interfering RNA (TNF-α-siRNA) and bone morphogenetic protein 2 (BMP-2)] were synthesized and transfected into RAW264.7 macrophages and pro-osteoblastic MC3T3-E1 cells, respectively. The target gene BMP-2, expressed on pro-osteoblastic MC3T3-E1 cells and silenced by the TNF-α gene on cells, was treated with titanium (Ti) particles that were assessed by real-time PCR and Western blot. We showed that recombinant adenovirus (Ad-siTNFα-BMP-2) can induce osteoblast differentiation when treated with conditioned medium (CM) containing RAW264.7 macrophages challenged with a combination of Ti particles and Ad-siTNFα-BMP-2 (Ti-ad CM) assessed by alkaline phosphatase activity. The receptor activator of nuclear factor-κB ligand was downregulated in pro-osteoblastic MC3T3-E1 cells treated with Ti-ad CM in comparison with conditioned medium of RAW264.7 macrophages challenged with Ti particles (Ti CM). We suggest that Ad-siTNFα-BMP-2 induced osteoblast differentiation and inhibited osteoclastogenesis on a cell model of a Ti particle-induced inflammatory response, which may provide a novel approach for the treatment of periprosthetic osteolysis.